1. Field of the Invention
The present invention relates to an improvement of a regenerative refrigerator having a regenerator.
2. Description of the Prior Art
FIG. 1 is a sectional view of a conventional regenerative refrigerator which is disclosed, for example, in Japanese Patent Publication No. 30433/71. In the same figure, the reference numeral 1 denotes a drive head, the numeral 2 denotes a cylinder mounted to the drive head 1, and the numeral 3 denotes a movable member which is driven for reciprocation within the cylinder 2 by means of the drive head 1 through an operating rod 4. In the interior of the movable member 3 is disposed a regenerator 5 which comprises phosphor bronze meshes or lead balls for example. In the upper and lower end portions of the movable member 3 there are formed gas passages 3a and 3b, respectively, which are in communication with the regenerator 5. Numerals 6 and 7 denote first and second closed chambers enclosed with the cylinder 2 and movable member 3 and formed respectively above and below the movable member. Numeral 8 denotes a seal for isolation between the first closed chamber 6 and the second closed chamber 7. The seal 8 is mounted in the upper end portion of the movable member 3 and is adapted to move together with the movable member while contacting the inner peripheral surface of the cylinder 2. Numeral 9 denotes a gap formed between the inner peripheral surface of the cylinder 2 and the outer peripheral surface of the movable member 3; numeral 10 denotes a heat transfer portion; numeral 11 denotes an expansion unit composed of the components 2 to 10; and numerals 12 and 13 each denote a gas pipe.
The operation of such conventional regenerative refrigerator will now be described. A high-pressure gas 15, e.g. helium, which has been compressed in a compressor (not shown) and discharged flows through the gas pipe 12 into the first closed chamber 6 of the cylinder 2, then passes through the gas passage 3a and is introduced into the regenerator 5, where it is cooled by chillness which was stored in the regenerator in the previous cycle. This cooled gas flows through the gas passage 3b into the second closed chamber 7. At this time, because of the presence of the seal 8, it is only a small amount of the gas that flows into the gap 9. The gas which has thus entered the second closed chamber 7 expands there and generates chillness to cool an object to be cooled (not shown) through the heat transfer portion 10. A portion of the gas which has become expanded and pressure-reduced in the second closed chamber 7 remains in the gap 9. On the other hand with movement of the movable member 3 into the second closed chamber, the other portion of the gas again passes through the gas passage 3b and then passes through the regenerator 5 in the direction reverse to the previous direction while being heat-exchanged with the regenerator to cool the regenerator. The gas thus heated by such heat exchange passes through the gas passage 3a and reaches the first closed chamber 6, from which it is introduced as an exhaust gas 14 into the foregoing compressor through the gas pipe 13, and is again compressed therein.
Since the conventional regenerative refrigerator is constructed as above, the gas remaining in the gap 9 can move freely, so convection is apt to occur under the influence of gravity. For example, when the regenerative refrigerator is mounted at such an angle as in FIG. 2 with respect to the gravitational directions, a part of the gas remaining in the gap 9 being low in temperature and high in density shifts to the lower side of the cylinder, resulting in that the temperature becomes lower on the lower side of the cylinder than on the upper side. If the regenerative refrigerator is mounted at such an angle as in FIG. 3, a low-temperature high-density portion of the gas remaining in the gap 9 shifts to the lower portion of the cylinder.
Thus, when the regenerative refrigerator is mounted at such an angle as in FIG. 2 or FIG. 3, as compared with the case where it is mounted at such an angle as in FIG. 1, there increases the loss of heat due to convection of the gas in the gap 9, thus causing deterioration of the refrigerating performance.